Question

Dim nm As String
Dim pass As String
nm = TextBox1.Text
pass = TextBox2.Text

Try
    cn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Pavilion\Documents\Visual Studio 2010\Projects\WindowsApplication5\Ent.accdb"
    cn.Open()
    Dim sql As String
    sql = "SELECT * FROM user WHERE UName='" & nm & "'AND Pwd='" & pass & "'"
    cmd = New OleDbCommand(sql, cn)
    dr = cmd.ExecuteReader
    While (dr.Read())
        If ((nm.Equals(dr(0))) And pass.Equals(dr(1))) Then
            MessageBox.Show("Login Sucessful")
        End If
    End While
Catch ex As Exception
    MsgBox("Login Failed :" & ex.Message)
End Try

此代码出现以下错误syntax error in FROM clause

Answer 1

如果您发布的代码是复制和粘贴的，那么您在用户名和AND关键字之间缺少空格。

您的代码：

"SELECT * FROM user WHERE UName='" & nm & "'AND Pwd='" & pass & "'"

应该是：

"SELECT * FROM user WHERE UName='" & nm & "' AND Pwd='" & pass & "'"

但是，您应该使用参数化查询来避免SQL注入攻击的可能性。像这样：

sql = "SELECT * FROM user WHERE UName=@nm AND Pwd=@pass"
cmd = New OleDbCommand(sql, cn)
cmd.Parameters.AddWithValue("@nm", TextBox1.Text)
cmd.Parameters.AddWithValue("@pass", TextBox2.Text)
cmd.CommandType = CommandType.Text
dr = cmd.ExecuteReader

Answer 2

@Tim是正确的，但我认为你的SQL可能也有问题，因为user是一个保留字。如果我执行

SELECT * FROM user WHERE UName='fred' AND Pwd='123'

SQL Server中的

我被告知Incorrect syntax near the keyword 'user'.

您可以通过在表名周围加上[]来克服这个问题，即

Select * FROM [user] WHERE UName='fred' AND Pwd='123'

Answer 3

Try

            cn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Pavilion\Documents\Visual Studio 2010\Projects\WindowsApplication5\Ent.accdb"
            cn.Open()
            Dim sql As String
            sql = "SELECT * FROM user WHERE UName='" + nm + "'AND Pwd='" + pass + "'"
            cmd = New OleDbCommand(sql, cn)
            dr = cmd.ExecuteReader
            While (dr.Read())
                If ((nm.Equals(dr(0))) And pass.Equals(dr(1))) Then
                    MessageBox.Show("Login Sucessful")
                End If
            End While
        Catch ex As Exception
            MsgBox("Login Failed :" & ex.Message)
        End Try

Answer 4

 "SELECT Firstname FROM [RegUser] where Firstname=@d3 and password=@d4"

我只是将我的表名括在方括号中并完成了操作。我希望这对您有很大帮助。

vb.net中FROM子句中的语法错误

4 个答案: